Method and apparatus for epoxy loc die attachment

ABSTRACT

A plurality of lead frames is supplied in lead frame by lead frame sequence. A curable adhesive, preferably a 505 Epoxy, is applied to one surface of each lead frame as it indexes through an application device. An attaching device attaches a device to each lead frame with the adhesive by holding the device in place to cure for a preselected period of time of about one second. Later, the lead frames have their edges trimmed and then are separated into separate lead frames.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 08/907,330,filed Aug. 6, 1997, now U.S. Pat. No. 6,051,449.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor device manufacture and,more particularly, to methods and structures for attaching semiconductordevices to lead frames.

2. State of the Art

During the manufacture of semiconductor devices, a semiconductor deviceor chip is often attached to a support, such as a lead frame. Ingeneral, a “leads-over-die” or “lead-on-chip” semiconductor deviceassembly has a lead frame with lead fingers that extend over the activesurface of the semiconductor device supporting the semiconductor devicebeing electrically connected to the bond pads located thereon, typicallyby wire bonds extending between the bond pads and the ends of the leadfingers, the other ends of the lead fingers for attachment to othercircuit components. The lead fingers extend inwardly on the lead frameto bond pads located on the active surface of the semiconductor devicefor connection thereto as described in U.S. Pat. No. 4,862,245 (Pashby,et al.) and U.S. Pat. No. 5,304,842 (Farnworth, et al.).

The semiconductor device may be attached to the lead frame usingadhesively coated tape as described in U.S. Pat. No. 5,304,842(Farnworth et al.) or by the use of hot or cold adhesives as describedin U.S. Pat. No. 5,286,679 (Farnworth et al.).

Use of hot or cold thermosetting or thermoplastic adhesives that haveheretofore been suggested affect the processing of the semiconductordevice assemblies as they require cure time for the adhesive and, inturn, cause delays in the manufacturing process to effect curing.

Therefore, it is desirable to have an adhesive for attaching thesemiconductor device to a lead frame which has the shortest desirablecure time for the adhesive to allow the manufacturing process toproceed.

SUMMARY OF THE INVENTION

A system for attaching a semiconductor device or die to each lead frameof a plurality of lead frames includes indexing means for supplying andadvancing the plurality of lead frames for semiconductor devices in alead frame-by-lead frame sequence. Each lead frame of the plurality oflead frames has an attaching surface to which a semiconductor device ordie is to be attached. The system also includes a source of curableadhesive. Application means are configured for receiving the pluralityof lead frames for semiconductor devices in the lead frame-by-lead framesequence. The application means is connected to the source of curableadhesive for receiving curable adhesive therefrom. The application meansis also configured for applying a metered amount of the curable adhesivein a preselected pattern to the application surface of each lead frameof the plurality of lead frames. The application means then supplies thelead frames with the curable adhesive applied thereto.

The system also includes a source of semiconductor devices to supplysemiconductor devices in a semiconductor device-by-semiconductor devicesequence. Attaching means are positioned relative to the source ofsemiconductor devices to obtain each semiconductor device of theplurality of semiconductor devices in the semiconductordevice-by-semiconductor device sequence. The attaching means is alsopositioned to receive the lead frames with the curable adhesive appliedthereto in lead frame-by-lead frame sequence from the application means.The attaching means is also configured to attach one of thesemiconductor devices to a corresponding lead frame of the plurality oflead frames in lead frame-by-lead frame sequence by urging the deviceinto contact with the curable adhesive of each lead frame of theplurality of lead frames and holding each of the semiconductor devicesin contact with the curable adhesive for a preselected period. That is,at least one semiconductor device is attached to each lead frame. Ofcourse, in some applications, multiple devices may be attached to aparticular lead frame configured to receive multiple semiconductordevices. Control means are provided in the system to supply operationsignals to operate the various components thereof.

The attaching means preferably includes press means for pressing eachsemiconductor device of the plurality of semiconductor devices intocontact with a curable adhesive. The attaching means also preferablyincludes transfer means for transferring each semiconductor device ofthe plurality of semiconductor devices in semiconductordevice-by-semiconductor device sequence from the source of semiconductordevices to the press means.

The press means desirably includes heating means to heat thesemiconductor device before it is pressed against the curable adhesive.The heating means is desirably a block positioned to receive eachsemiconductor device of a plurality of semiconductor devices from thetransfer means. The press means most preferably includes a pressmechanism to move the block from a receiving position to receive thereona semiconductor device of the plurality of semiconductor devices into anattached position in which the block with a semiconductor device of theplurality of semiconductor devices is urged into contact with thecurable adhesive. The heating means desirably heats the block to atemperature from about 200° C. to about 225° C.

The curable adhesive is most preferably a snap curable epoxy having acure time of substantially less than one minute and most preferablyhaving a cure time of less than one second. In a preferableconfiguration, it is desirable that the curable adhesive have a fillermaterial included therein. The filler material may be anyelectrochemically neutral material but is preferably a granulatedTeflon®.

The application means is configured to apply about one milligram of thecurable adhesive to each lead frame. The application means may alsoinclude a structure positioned to contact the application surface of alead frame for applying the curable adhesive thereto. The applicationmeans may include a roller having portions positioned to selectivelycontact the application surface of the lead frame and the opposingsurface. Alternately the application means may include a printingstructure to contact the application surface of the lead frame or theactive surface of the semiconductor device. The printing structure mayinclude a plate, a silkscreen die, or the like. The application meansmay also optionally include one or more nozzles positioned to depositthe curable adhesive in a desired location on either the lead frame orthe active surface of a semiconductor device.

In alternate configurations, the lead frames of the plurality of leadframes are connected one to another. The lead frames preferably have atleast one and preferable two removable edges, or rails, with driveperforations formed therein. Indexing means includes an electricaldevice connected to a drive structure which is configured to engage theperforations formed in each lead frame.

The attaching means preferably includes an anvil sized for positioningopposite the block and spaced therefrom to receive each lead frame ofthe plurality of lead frames therebetween. The anvil functions tosupport each lead frame as the semiconductor device is pressed againstthe application surface. An anvil may also be positioned opposite theapplication means to support each lead frame as the curable adhesive isapplied thereto.

A method for applying curable adhesive to each lead frame of a pluralityof lead frames and attaching a semiconductor device to each such leadframe includes providing a system and operating the system to supplysemiconductor devices and lead frames relative to application means andattaching means. The system is also operated to apply adhesive to asemiconductor device site of each lead frame and to then attach asemiconductor device to the adhesive at the semiconductor device site.Preferably, the adhesive is a snap curable epoxy with a cure time ofabout 1 second. Even more preferably, the application means includes apressing structure which includes a block that heats the semiconductordevices to a temperature from about 200 degrees centigrade to about 225degrees centigrade.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings which illustrate what is presently regarded as preferredmodes of carrying out the invention:

FIG. 1 is a simplified diagram of a system of the invention;

FIG. 2 is a printing structure of the system of the invention of FIG. 1for printing adhesives onto a lead frame;

FIG. 3 is a cross section of FIG. 2 taken at the section 2—2;

FIG. 4 shows an adhesive application nozzle for use in a system of theinvention positioned relative to lead frames;

FIG. 5 is a perspective view of multiple adhesive application nozzlesfor use in a system of the invention positioned relative to lead frames;

FIG. 6 shows a roller printing mechanism for use in a system of theinvention for applying adhesive to lead frames;

FIG. 7 is a partial perspective view of a roller system comparable tothat shown in FIG. 6 for applying adhesive to lead frames;

FIG. 8 is a perspective view of a pick-up head of the transfer mechanismfor transferring devices of the system of FIG. 1;

FIG. 9 is a simplified perspective view of a block of the applicationmeans of a system of the invention;

FIG. 10 is a perspective view of an indexing system for use with asystem of the invention with a plurality of lead frames depictedpartially cut-away and in perspective; and

FIG. 11 is a block diagram of a method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to drawing FIG. 1, a system 10 is illustrated for attaching asemiconductor device to each lead frame of a plurality of lead frames toform a corresponding plurality of semiconductor device assembliessuitable for use in various electronic circuits.

The system 10 includes indexing means for supplying and advancing aplurality of lead frames for semiconductor devices in a leadframe-by-lead frame sequence. More specifically, the lead frames 12 aresupplied from a source 14 and are urged or moved relative to the otherstructures of the system by a driver 16, which is constructed todrivingly engage and move the plurality of lead frames in leadframe-by-lead frame sequence, all as more fully discussed hereinafter.

The system 10 also includes a source of curable adhesive 18. The sourceof curable adhesive 18 includes a reservoir 20 interconnected by conduit22 to an electrically driven solenoid 24. The solenoid 24 is connectedby conductor 26 to control means, such as controller 28, to receiveoperation signals therefrom to cause the solenoid 24 to move between aclosed position and an opened position. The solenoid 24 may be anysuitable solenoid which remains open for a selected period of time sothat, given the pressure of the adhesive in the conduit 22, a meteredamount is thereby dispensed. Alternately, some other metering device maybe used that dispenses the curable adhesive in metered quantities. Forexample, a gear pump or piston pump may be used to dispense meteredamounts of curable adhesive. The adhesive from the source of curableadhesive 18 proceeds through the delivery conduit 30 when the solenoid24 is in the open position. That is, adhesive from the reservoir 20 isurged by any appropriate pressure generating arrangement, including anadhesive pump, air pressure and the like, through the conduit 22 andthrough a delivery conduit 30 of an application means 32.

The application means 32 is configured to receive the plurality of leadframes 12 in lead frame-by-lead frame sequence. The application means 32is connected to the source of curable adhesive 18 to receive curableadhesive therefrom through the delivery conduit 30. The applicationmeans 32 is configured and operable to apply the metered amount ofcurable adhesive in a preselected pattern to the application surface 36opposite a second surface 34 of each lead frame of the plurality of leadframes 12 (FIG. 10). As depicted in FIG. 1, the application means 32includes an applicator 38 which is here operated in an up and down or inand out direction 40 by a rod 42 connected to a piston 44 positioned ina cylinder 46. The piston 44 is here shown to be fluid driven and may beoperated by gas or liquid. However, a gas is preferable because offaster response times, and air is preferable because of low cost.

As illustrated in drawing FIG. 1, air under pressure is received from areservoir 48 via a first supply line 50 through a first air solenoid 52and a connector 54 to the cylinder 46. A second air solenoid 56 isconnected to receive air under pressure via a second supply line 58. Thesecond air solenoid 56 is connected by a connector 60 to the cylinder46. In operation, air under pressure is supplied to the reservoir 48,for example, by an on-demand air pump 62. That is, the air pump 62 mayoperate under the control of the controller 28 or upon detection of apressure signal indicating a need to increase the pressure in thereservoir. To operate the applicator 38, the air solenoids 52 and 56 areoperated by operation signals received from the controller 28 viaconductors 64 and 66 so that air under pressure is supplied to theunderside 68 of the piston 44 in order to urge the applicator 38 upward40 toward one of the plurality of lead frames 12. As air under pressureis being supplied to the underside 68 of the piston 44, the air solenoid56 is positioned to vent air from the top 70 of piston 44 to theatmosphere from the vent 71. When it is desired to have the applicator38 move away from the plurality of lead frames 12, the air solenoid 52is positioned to a venting position in order to vent air through vent72. At the same time, air under pressure may be directed through the airsolenoid 56 via the second supply line 58 and the connector 60 to thetop 70 of the piston 44 in order to urge it in a downward direction. Asso configured, it can be seen that the piston 44 and, in turn, theapplicator 38 may be positioned precisely as desired based on theoperation signals received from the controller 28 in order to effect atransfer of adhesive supplied via the delivery conduit 30 to theapplicator 38 upon coordinated operation of the solenoid 24.

It may be noted that a first air solenoid 52 and a second air solenoid56 are here depicted. However, it can be seen that a three-way solenoidvalve may be used in lieu of the first air solenoid and the second airsolenoid. Further, other mechanisms may be used to meter air or someother suitable fluid to and from the cylinder 46 to regulate themovement of the piston 44.

The system 10 illustrated in drawing FIG. 1 also includes a source ofsemiconductor devices 74, which is here illustrated only in part as asimple conveyor 76 with a plurality of semiconductor devices 78positioned thereon. A stepper motor 80 may be operated to cause theconveyor 76 to move the semiconductor devices 78 in a direction 82toward the attaching means 86. The stepper motor 80 is connected by aconductor 84 to receive operation signals from the controller 28 to, inturn, cause each device of the plurality of semiconductor devices 78 onthe conveyor 76 to index toward the attaching means 86 in coordinationor in synchronization with movement of the plurality of lead frames 12.

The attaching means 86 is positioned relative to the source ofsemiconductor devices 74 to obtain each semiconductor device of theplurality of semiconductor devices 78 in the semiconductordevice-by-semiconductor device sequence. The attaching means 86 also ispositioned relative to the plurality of lead frames 12 to obtain eachlead frame in lead frame-by-lead frame sequence. The attaching means 86is also configured to attach one semiconductor device of the pluralityof semiconductor devices 78 to a corresponding one lead frame of theplurality of lead frames 12 in a lead frame-by-lead frame sequence byurging each semiconductor device 78 into contact with the curableadhesive positioned on the one corresponding lead frame of the pluralityof lead frames 12. The attaching means 86 further is operable to holdeach semiconductor device of the plurality of semiconductor devices 78in contact with the curable adhesive for a preselected period of time.

The attaching means 86 illustrated in drawing FIG. 1 is a simplifieddepiction of a mechanical system that can be assembled to be operated bya control means, such as the controller 28 in order to effect desiredoperations. The attaching means 86 illustrated includes transfer means88 which is here depicted to be a mechanism with an arm 90 attached tohousing 92, both of which are rotatable by driving a gear 96 thatinterconnects with an appropriate plurality of matching gear elements 97associated with the housing 92. More specifically, the gear 96 has teeth95; and the gear elements 97 are recesses to drivingly receive the teeth95. In operation, the gear teeth 95 and the recesses 97 are configuredto cause the housing 92 to rotate about rod 112 upon activation of thestepper motor 94. The stepper motor 94 is connected to the controller 28by conductor 93 to receive operation signals from the controller 28 tocause the stepper motor 94 to rotate between a pick up position in whichthe arm 90 is operated to pick up a device of the plurality ofsemiconductor devices 78 and a release position in which thesemiconductor device that has been picked up is deposited on the block110. Of course, the relationship between the housing 92 and gear 96 maybe any desired mechanical or electromechanical arrangement to effectoperation of the housing 92 and, in turn, cause the arm 90 to rotate.

The arm 90 has a pickup 98 which is connected through a conduit 100 andthrough a solenoid 102 to a reservoir 104 and a vacuum pump 106. Thevacuum pump 106 is operated to create a desired vacuum in the reservoir104. Upon operation of the solenoid 102, by receipt of operation signalsfrom controller 28 via conductor 108, a vacuum is applied through theconduit 100 to the pickup 98. The conduit 100 extends inside the housing92, the arm 90 and extension 91 to create a vacuum to pick up eachdevice of the plurality of semiconductor devices 78 on the conveyor 76.The pickup 98, as more fully described hereinafter, is positionedproximate each semiconductor device of the plurality of semiconductordevices 78 and picks it up by vacuum in order to reposition thesemiconductor device of the plurality of semiconductor devices 78 on ablock 110.

The transfer means 88 also includes a vertical positioning structurewhich includes a rod 112 rotatably attached to the housing 92 at theupper end 114. The rod 112 has appropriate teeth 116, configured tointeract with drive teeth 118, associated with a gear 120. The gear 120is driven by a stepping motor 122 shown in phantom. The stepping motor122 is driven electrically by operation signals received via conductor124 from the controller 28.

In operation, the transfer means 88 can be moved upwardly and downwardlyor inwardly and outwardly 126 by operation of the stepping motor 122. Inturn, the arm 90 and the pickup 98 can be moved into close proximity orcontact with each semiconductor device of the plurality of semiconductordevices 78. When in virtual contact, appropriate vacuum can be appliedby operation of the solenoid 102 so that the semiconductor devices 79under the pickup 98 may be picked up and raised upon operation of thestepping motor 122. When raised upwardly 126 an appropriate distance128, the housing 92 may be rotated by operation of the stepper motor 94through gear 96 and recesses 97. Thus each semiconductor device of theplurality of semiconductor devices 78 may be transferred from the sourceof semiconductor devices 74 to the block 110.

It may be recognized that the transfer means 88, herein described, issimply illustrative of structure to effect the transfer of eachsemiconductor device of the plurality of semiconductor devices 78 to theblock 110. A variety of chutes, slides and similar mechanisms may bedevised to effect the positioning of each semiconductor device of theplurality semiconductor device 78 in a sequential fashion onto block110.

The attaching means 86 also includes a press mechanism to move eachsemiconductor device of the plurality of semiconductor devices 78 intocontact with the curable adhesive. The illustrated mechanism has a block110 shown in its receiving position in which it receives a semiconductordevice of the plurality of semiconductor devices 78. The press mechanismis operable from the receiving position illustrated in drawing FIG. 1 toan attaching position in which block 110 is positioned upwardly towardthe plurality of lead frames 12 to contact the curable adhesive 132associated with the lead frame that has been indexed to be positionedrelative to the attaching means 86 and, more particularly, the pressmechanism. That is, a semiconductor device, such as a semiconductordevice of the plurality of semiconductor devices 78 and, morespecifically, the semiconductor device 130 shown in phantom on the block110, is urged upwardly to be in contact with the curable adhesive 132that has been positioned on each lead frame of the plurality of leadframes 12 by the application means 32.

The press mechanism illustrated in drawing FIG. 1 is a hydraulicallyoperated cylinder 134. The hydraulic fluid in the illustratedarrangement of drawing FIG. 1 may be air supplied from a reservoir 136through a raised solenoid 138 and a lower solenoid 140. That is, airpressure may be created in the reservoir 136 by operation of an air pump144. The air pressure may be supplied via supply lines 146 and 148 totheir respective solenoids 138 and 140. The solenoids 138 and 140 may beoperated in sequence to place air pressure underneath the piston 135.Air under pressure under the piston 135 urges the piston 135 upwardly orinwardly while solenoid 140 is operated to vent the air above the piston135 through a vent line 150 to the atmosphere. Similarly, when the block110 is to be lowered, the solenoid 140 is operated to provide airpressure to the top part of the piston 135 to urge it downward while theraised solenoid 138 is operated to vent the air thereunder through ventline 152. The solenoids 140 and 138 are connected by conductors 154 and156, respectively, to the controller 28 to receive operation signalstherefrom in order to effect movement of the piston 135 and, in turn,the block 110. Of course, the air pressure is maintained by appropriateoperation of the air pump 144 by receipt of operation signals viaconductor 158 from the controller 28 or from a pressure sensor asdesired. The solenoids 140 and 138 may be replaced with a three-waysolenoid or by other mechanisms to port air or other hydraulic fluid.

The block 110 is here shown with a spring wound electrical conductor 160extending away therefrom. The conductor 160 is spring wound so that theblock 110 may easily move upward and downward, as described. The springwound conductor 160 is connected to a source of electrical power and toa heater 111 (FIG. 9), positioned in the block 110, so that the blockmay be heated to a desired temperature. In turn, a semiconductor device,such as semiconductor device 130, is heated in the process of moving itand holding it in place against the curable adhesive 132 to a desiredtemperature in order to effect the curing of the curable adhesive 132 asthe semiconductor device 130 comes into contact therewith.

The applicator 38 of the application means 32 is illustrated in moredetail in drawing FIGS. 2 and 3. It receives adhesive from the deliveryconduit 30 under pressure from the reservoir 20. That is, the adhesiveis urged into a distribution chamber 162 so that it may be urged outthrough a plurality of apertures such as aperture 164. The top 166 ofthe applicator 38 has a plurality of apertures, such as aperture 164,formed therein in a desired pattern. For example, the applicator 38 hasan illustrated pattern of apertures 165 which is desired in order toreceive and hold a particular device in contact with the bumps orconnector pads of a lead frame containing electrical leads in a desiredpattern. The apertures 165 may be of different sizes and dimensions, aswell as in different geographic configuration, all to effect the desiredapplication of adhesive.

In operation, the applicator 38 will be brought into very closeproximity to the application surface 36 of a particular lead frame ofthe plurality of lead frames 12 being indexed by driver 16. Adhesive isurged through the delivery conduit 30 to the distribution chamber 162.Adhesive is thereupon urged outward through the apertures 165 to contactand adhere to the application surface 36 of each lead frame of theplurality of lead frames 12. As each lead frame of the plurality of leadframes is indexed past the applicator 38, the applicator 38 is firstretracted and then positioned upward to cause the adhesive to contactthe surface of the lead frame and position the adhesive thereon in thedesired pattern.

In drawing FIG. 1, there is illustrated a substantial distance betweenthe application means and the attaching means. That is, time to curecould be provided by providing an appropriate or desired distance 268between the application means 32 and the attaching means 86. The delay,in turn, can provide time for the adhesive to begin to set up or startits curing process.

Referring to drawing FIGS. 4 and 5, an alternate arrangement of aplurality of lead frames is illustrated in which a plurality of nozzlesincluding nozzles 178, 186 and 188 is shown positioned to apply adhesiveto the application surface 171 of lead frames 172, 174 and 176. Thus, itcan be seen that the nozzles 178, 186, 188 may provide a desired patternof adhesive 190, 192 and 194 as illustrated in drawing FIG. 5. Eachnozzle 178, 186 and 188 is connected to the common delivery conduit 30for further connection through the solenoid 24 to the reservoir 20 ofcurable adhesive.

Referring back to drawing FIG. 2, it can been seen that the applicator38 is, in effect, a type of printing mechanism, a portion of whichapplies adhesive to the underside or to one surface of each lead frameof a plurality of lead frames. In lieu of patterned apertures, such asthat illustrate in drawing FIGS. 2 and 3, a silk screen structure may beprovided over the distribution chamber 162 so that the adhesive may passthere-through in a desired pattern provided in the silkscreen surface.

In drawing FIGS. 6 and 7, a roller mechanism is illustrated. Morespecifically, a plurality of lead frames 196 is shown passing relativeto a roller 200. The roller 200 is driven by a stepping motor, splitphase motor or the like, 202 which is connected by a conductor 204 tothe controller 28 to receive operation signals therefrom. The roller 200is positioned in a container 206 which has there within a quantity ofcurable adhesive 208. As the roller rotates 210 through the adhesive208, it picks up adhesive on desired adhesive application surfaces. Morespecifically, as can be better seen in drawing FIG. 7, raised surfaces212 and 214 are provided. A wiper 216 is positioned in close proximityto the roller 200 in order to wipe all excessive adhesive therefrom andreturn it to the container 206. As seen in drawing FIG. 7, the wiper 216has a first notch 218 and a second notch 220 to register with the raisedsurfaces 212 and 214, respectively. The notches 218 and 220 are inset adistance 222 so that the appropriate metered amount of adhesive willremain on the surfaces 212 and 214. In turn, as the roller 200 rotatesinto contact with a lead frame of a plurality of lead frames 196,adhesive on the surfaces 212 and 214 is deposited on each lead frame ofthe plurality of lead frames in a desired pattern. That is, the adhesiveis applied at a desired site on the desired surfaces of each lead frame.A plurality of spaced apart surfaces, such as surfaces 212 and 214, maybe positioned around the perimeter of the roller 200 based on thedimensions of the lead frame and the diameter of the roller 200.

It may be understood that a variety of other systems and structures maybe provided in order to apply the adhesive to the underside or to onesurface of each lead frame of a plurality of lead frames. In addition tomethods or systems herein illustrated or described, one may be able tospray or shoot adhesive in order to effect a desired contact in apreferred pattern.

As hereinbefore discussed, each semiconductor device of the plurality ofsemiconductor devices 78 is to be transferred from the source ofsemiconductor devices 74 to the block 110. The pickup 98 in drawing FIG.1 is better illustrated in drawing FIG. 8. The pickup surface 230 ishere shown to be a flexible surface with a plurality of small holes 232.The pickup surface 230 may be better described as a porous surfacethrough which air may readily be drawn. Thus the creation of a vacuum inthe chamber 234 is transmitted to external the pickup surface 230wherein suction upon contact with a semiconductor device of theplurality of semiconductor devices 78 is sufficient to hold thesemiconductor device against the pickup surface 230. Such semiconductordevice may then be retained against the pickup surface 230 and liftedand transferred from the conveyor 76 to the block 110. As can be seen,the vacuum is effected through an internal channel 236 formed in theextension 238 which is connected to the pickup 98.

Turning now to drawing FIG. 10, it can be seen that a plurality of leadframes 12, illustrated in drawing FIG. 1, is here shown consisting oflead frames 240, 242, 244 and 246. Each of the lead frames 240, 242, 244and 246 has a plurality of lead fingers such as lead finger 248. Eachlead frame 240, 242, 244 and 246 is secured with the others by at leastone and preferably two outside edges, or rails, 250 and 252 formed withperforations 254 to mesh with drive teeth 256 and 258 associated withdriver 16. The driver 16 is driven via axle 260 by a driver motor 266which is connected by conductors 268 and 270 to the controller 28 inorder to cause the plurality of lead frames 12 to index or to moverelative to the application means 32 and the attaching means 86 asdesired. As here shown, the driver 16 has an internal recessed portion272 which allows the lead frames with a respective device or devices orsemiconductor chips 274, 276 and 278 attached thereto to pass there overfor further processing in which the lead frames are separated one fromthe other and wherein the outside edges 252 and 250 are separatedtherefrom.

It can be seen herein and as illustrated in drawing FIG. 11 that tooperate the illustrated system, the user needs to provide a system suchas that illustrated in drawing FIG. 1. In operation, the controller 28is activated by positioning an on/off switch such as on/off switch 280to an on position. Appropriate speed or rate information is selected byoperation of the dial 282 relative to an index. Other mechanisms may beused to input the speed or rate of operation that is desired. A varietyof computers or similar electronic devices may be used to generate thenecessary operation signals to operate the various devices hereinthrough various electromechanical devices. The control means may bepowered from an external source via a power cord 284.

The control means sends the necessary operation signals in order tocause adhesive to process through the solenoid 24 and the deliveryconduit 30 to the applicator 38. The applicator 38 is moved up towardand away from the appropriate lead frames in order to apply a pattern ofadhesive to one surface, more particularly, the application surface 36of each lead frame of a plurality of lead frames in a lead frame-by-leadframe sequence. Semiconductor devices such as device 78 are supplied bya source and transferred by attaching means which includes a transferstructure to a press mechanism. That is, the semiconductor devices, suchas semiconductor device 79, are transferred to the press mechanismwhich, in turn, urges each semiconductor device in semiconductordevice-by-semiconductor device sequence to and in contact with thepatterned adhesive.

It should be noted that the preferred adhesive is a snap cure adhesiveavailable from Quantum Materials, Inc. of San Diego, Calif. A preferredadhesive has been determined to be a snap cure epoxy which is known asthe 505 epoxy formula. The desired snap cure epoxy is preferably definedto have a cure time of substantially less than one minute and preferablyless than one second when it is applied with a block 110 that ispreferably at a temperature between 200° and 225° C. That is, the block110 is heated via conductor 160 to expedite the curing when thesemiconductor devices are being attached to the attaching surface ofeach of the plurality of lead frames.

The snap cure epoxy and, more particularly, the 505 epoxy is preferredin metered amounts of about 1 milligram for every device site or forevery device that is being applied to the lead frame. In someapplications, multiple devices may be applied. In others, a singledevice may be applied.

In preferred arrangements, the epoxy applied preferably contains anon-conductive filler which may be made of Teflon®. Teflon® granularmaterial or flakes may be mixed into the adhesive in order to functionas a filler to achieve the desired tackiness and cure time.

The application means is preferably operated to apply the necessaryamount of adhesive at each semiconductor device site. When asemiconductor device is pressed against the semiconductor device site,the adhesive is pressed to have a thickness of approximately 0.001 inch.

Other curable adhesives comparable to the 505 epoxy that are snapcurable in one minute or less, and preferably one second or less, may besuitable.

Mechanisms for applying adhesive may include wiping mechanisms or otherdevices to clean away excess material to avoid contaminating differentlead frames with excess adhesive material. Those skilled in the art willrecognize that the embodiments are merely illustrative of the principlesof the invention.

What is claimed is:
 1. A method of attaching a semiconductor device to alead frame, said method comprising: providing a source of snap curableadhesive; providing a source of lead frames, each lead frame having anattaching surface; providing a source of semiconductor devices, eachsemiconductor device having an active surface; applying said snapcurable adhesive to a portion of one of the lead frames; and contactinga portion of said active surface of one of the semiconductor deviceswith said portion of one of the lead frames.
 2. The method of claim 1,further including the step of: heating one of said semiconductordevices.
 3. The method of claim 1, wherein said snap curable adhesiveincludes a snap curable epoxy having a cure time of about one second. 4.The method of claim 1, wherein said snap curable adhesive includes anadhesive having a cure time of substantially one minute or less.
 5. Themethod of claim 1, wherein said snap curable adhesive is applied to theportion of said one of the lead frames using a roller.
 6. A method ofattaching a semiconductor device to a lead frame, said methodcomprising, the steps of: providing a source of snap curable adhesive;providing a source of lead frames, each lead frame having an attachingsurface; providing a source of semiconductor devices each semiconductordevice having an active surface; applying said snap curable adhesive toa portion of the active surface of one of said semiconductor devices;and contacting said snap curable adhesive with a portion of one of saidlead frames.
 7. The method of claim 6, wherein said snap curableadhesive includes an adhesive having a curing time of about one secondor less.
 8. The method of claim 6, wherein said snap curable adhesive isapplied to said active surface of one of said semiconductor devices in apredetermined pattern.